When Sheila McClelland picked up a Pug named Obi a year ago, he had a three-centimetre tumour on his front leg. Immediately, McClelland took him to see a veterinarian.

'It turned out to be cancer, and amputation was the only option,' says McClelland, who is the founder of Lifelong Animal Protection, a charity that rescues companion animals in Hong Kong.

'Initially, I was very upset but when we found out the tumour was localised and it could be dealt with [through an amputation] I was happy that we could give him a future.'

As with any surgery, McClelland says, there is always a risk of complications or death. However, the risk of complications was low for Obi, and considerably less than leaving the tumour there, she says.

'The tumour must have given him some irritation, so after the surgery, he seemed very perky and overjoyed. It took him less than a day to balance on three legs,' McClelland recalls.

She has also been taking care of Mimi, a black-haired Pomeranian Cross, for the past five years. Initially, she was found paralysed in her back legs. 'She had been dragging her legs along and they were covered in lesions and abrasions,' McClelland says. 'We established that it wasn't something that could be cured, so the best thing would be to get a wheelchair for her.'

At first, one of McClelland's friends made a wheelchair out of a shopping cart, but it was made of steel and too heavy for Mimi's small body. Then McClelland found a lightweight aluminium wheelchair for dogs on the internet. 'You don't know if a dog will take to a wheelchair, but when we put her in it, she was off like the wind.

'Dogs are phenomenally resilient. They have no concept of being different or disabled,' she says.

Veterinarian Michael Bradley, at Stanley Vet Clinic, says the most prevalent reason for amputations among dogs and cats is severe trauma.

'Dogs are hit by cars, cats jump out of windows or they fall from heights,' he explains. '[Amputations] are not as uncommon as you think. If there is a very severe trauma, an amputation is the quickest and cheapest way of getting an animal back to a reasonable quality of life.'

He adds bones that are fractured and broken in multiple places may require numerous plates and screws that could 'put the animal through a lot of pain'.

When it comes to amputating a limb, it's not viewed as a complicated procedure. 'It's quite major surgery, but cutting through large muscles and nerves is not overly complicated,' he explains.

The other main cause of amputations for dogs, Bradley says, is bone tumours with osteosarcoma the most common type. As many large breed dogs, such as Irish Wolf Hounds, are susceptible to bone cancers, the veterinarian says tumours are 'incredibly painful so we'll amputate to take it away'.

'They heal really quickly,' Bradley says. 'When they get home, you should give them some basic physiotherapy, just to get them used to walking on three legs. Quite often, once [an animal's] leg is amputated, it gives them a better quality of life than before, since it was probably in pain.'

One side effect of amputating a leg is adding pressure on other limbs, particularly for big breed dogs. The result is a predisposition to arthritis, the veterinarian says.

For pets that have to go under the knife, most seem happier after the surgery. 'Animals don't wallow in self-pity. They have survival instincts, so they don't have time to do that,' says Janice Jensen, director at Hong Kong Animal Speak. 'Undergoing an amputation doesn't change who they are. If you have cancer you are probably feeling pretty bad and in a lot of discomfort. [After surgery] you will have a happier animal.

'It's a remarkable thing to watch. If you can get past the look [of a missing limb], then is there no difference between them and a [four-legged] animal.'

As for Obi, he was adopted into a family last month. 'There is nothing different about Obi,' McClelland says. 'It's more about us not him. Obi is just so normal we forget about it.'